量測

量測是許多圖像解譯問題中的重要功能。兩種測量方式很重要。首先是距離和高度的測量，進而是體積和麪積的測量。進行此類測量的實踐構成了攝影測量的主題（第 3 章），它將圖像幾何知識應用於推導精確距離。雖然嚴格來説，攝影測量僅適用於照片的測量，但通過擴展，它具有類似物，用於從其他類型的遙感圖像推導測量。

第二種測量形式是對圖像亮度的定量評估。測光科學致力於測量光的強度，包括通過使用稱為密度計的特殊儀器檢查圖像色調來估計場景亮度。如果測量的輻射超出可見光譜，則適用術語輻射測量。光度學和輻射度學都應用相似的儀器和原理，因此它們密切相關。

Measurement, or mensuration, is an important function in many image interpretation problems. Two kinds of measurement are important. First is the measurement of distance and height and, by extension, of volumes and areas as well. The practice of making such measurements forms the subject of photogrammetry (Chapter 3), which applies knowledge of image geometry to the derivation of accurate distances. Although, strictly speaking, photogrammetry applies only to measurements from photographs, by extension it has analogs for the derivation of measurements from other kinds of remotely sensed images.

A second form of measurement is quantitative assessment of image brightness. The science of photometry is devoted to measurement of the intensity of light and includes estimation of scene brightness by examination of image tone, using special instruments known as densitometers. If the measured radiation extends outside the visible spectrum, the term radiometry applies. Both photometry and radiometry apply similar instruments and principles, so they are closely related. ^[1]